Membrane oxygenator



Dec. 16, 1969 G. MON ETAL 3,484,211'

MEMBRANE OXYGENATOR Filed Dec. 8. 1964 v 2 Shee'lzs--SheeI l 2 INvENToRs GEORGE MON KENNETH E. WOOD ARD 2 Sheets-Sheet 2 ATTORNEYS Dec. I6, 1969 GvoN ETAL MEMBRANE OXYGENATOR Filed Dec. 8. 1964 GEORGE MON KENNETH E. WOODWARD A o l EE ffl/WM,

BY ggf i United States Patent O MEMBRANE OXYGENATR George Mon, Washington, D.C., and Kenneth E. Woodward, McLean, Va., assignors to the United States of America as represented by the Secretary of the Army Filed Dec. 8, 1964, Ser. No. 416,937

Int. Cl. A61b 19/00 US. Cl. 23--2585 8 Claims ABSTRACT OF THE DISCLOSURE A membrane oxygenator having a plurality of modules stacked on top of each other. Each module consists of' an upper plate and a lower plate with a membrane pervious to oxygen and carbon dioxide and impervious to blood placed therebetween. The lower plate in each module includes a passage for blood with the circumference of the passage being defined by a sealing ring. When the module is assembled and the plates placed together, the sealing ring defines a passage for gas flow on the surface of the upper plate as well, with the blood and gas passages being separated by the membrane. Each plate has the appropriate openings for the entrance and exit of blood or gas. When the modules are stacked to form an oxygenator assembly, the openings are aligned so that there are single channels for blood entrance, blood exit, gas lentrance and gas exit, respectively. Each module contains a water passage to keep the blood at the desired temperature level. A fluid amplifier is used to provide gas ow into the oxygenator and may be oscillated to provide a pulsating flow.

The invention described herein may be used by or for the Government of the United States for governmental purposes without the payment to us of any royalty thereon.

This invention relates generally to a membrane oxygenator device and, more particularly, to an improved membrane oxygenator for providing arterialized blood.

The technique of performing surgery on the heart and its related vessels has been advanced steadily through the years. One of the major reasons for this advance lies in the development of artificial extra-corporeal circulation devices and methods for oxygenating venous blood.

Oxygenation of venous blood can be accomplished by a variety of methods. These methods rely on a gas exchange process wherein carbon dioxide is removed from the blood while oxygen is added thereto. For instance, one common method of blood oxygenation involves direct contact between an oxygen-carrying gas and a film of blood to accomplish the gas exchange. However, a thin film of blood is difficult to maintain on many chemically inert surfaces. Also, it is sometimes difiicult to control the atmosphere to which the blood film is exposed.

Another direct contact approach which has been successfully utilized to a certain extent involves the theory of bubble oxygenation. Devices based on this principle of oxygenation, wherein oxygen is bubbled through the blood, can cause foaming of the blood, which is undesirable.

Another type of blood oxygenator utilizes a membrane which is pervious to oxygen and carbon dioxide but impervious to blood. Such devices can provide a large surface area for oxygenating purposes while still keeping the blood in a closed unit. It is in this general area of oxygenators that the instant invention applies.

In the apparatus of the present invention, a first plate is provided having a blood passage and a water passage. A second plate, adapted to provide a gas passage when placed on the first plate, combines with the first plate to till 3,484,211 Patented Dec. 16, 1969 make a single module. A semipermeable membrane extends between both plates of the module defining a blood passage on one side of the membrane and a gas passage on the other side of the membrane. The first plate containsl suitable sealing materials to preclude leakage of the circulating fluids. Both plates of the module have appropriate openings for passage of blood, oxygen and water.

A complete integrated oxygenator comprises a plurality of modules stacked one on the other between a top and bottom plate adapted for connection to exterior sources of uids. This module arrangement provides for parallel oxygenation of the blood between each pair of plates of each module.

Accordingly, a principal object of the present invention is to provide an improved blood oxygenator.

Another object of this invention is to provide a method and means for improving the gas exchange characteristics of a blood oxygenator.

A further object of this invention is the provision of a membrane oxygenator which minimizes the problem of blood clotting.

Still another object of this invention is the provision of a pair of plates with a membrane sandwiched therebetween for the oxygenation of blood.

A still further object of this invention is to provide an improved membrane oxygenator that minimizes foaming or bubbling of blood.

Still another object of this invention is the provision of a plurality of stacked modules, each module comprised of a pair of plates, for increasing the surface area of membrane oxygenators.

A still further object of this invention is to provide means for maintaining the temperature of the blood in a membrane oxygenator at a desired level.

Still another object of this invention is to improve the gas exchange process of membrane oxygenators by presenting a very thin film of blood for oxygenation.

A still further object of this invention is to provide an extracorporeal circulation device which can be used as a dialyzer.

Still another object of this invention is to provide an improved method for oxygenating venous blood.

A still further object of this invention is the provision of an improved method for operation of a blood oxygenator, utilizing a plurality of parallel blood flow paths for rapid gas exchange.

Still another object of this invention is to provide a membrane oxygenator that can operate with either steady or pulsed gas and blood tiows.

A still further object of this invention is the provision of a membrane oxygenator in which the oxygen gas can be controlled above, below or at atmospheric pressure levels.

Further objects and advantages of the present invention will become readily apparent as the following detailed description of the invention unfolds and when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a top plan view of a bottom or blood plate which forms part of the present invention;

FIG. 2 is a longitudinal cross-sectional view taken along the line 2 2 of FIG. 1;

FIG. 3 is a top plan view of the top or gas plate which forms part of the present invention;

FIG. 4 is a longitudinal cross-sectional view taken along the line 4 4 of FIG. 3;

FIG. 5 is a longitudinal cross-sectional view of the gas and blood plates with a membrane sheet sandwiched therebetween; and

FIG. 6 is a diagrammatic perspective view of a plurality of modules sandwiched between a top and bottom plate for connection to blood, gas and water sources for integrated oxygenator operation.

Referring now to the plates comprising the present invention, there is shown in FIGS. l and 2 a plate 10 machined for blood ow, as well as water ow when such is desired. This first plate, which is preferably the bottom plate of the pair of plates making up a module, can be considered as the blood plate. The plate is shown in FIGURE 1 as being of reduced dimensions for purposes of illustration. In an operative embodiment, the plate 10 consisted of a piece of 1A plexiglass, 9 wide and 14 long.

Machined in the top of the plate 10 is a passage 12 for blood flow, the passage 12 running substantially the full length of the plate 10 and a major portion of its width, while being of a small depth. The depth of the passage 12 is exaggerated for purposes of illustration. On the longitudinal ends of the passage 12 are blood manifolds 14 and 16 comprised of narrow transverse chambers 18 and respectively. The manifold 14 also contains a plurality of holes 22 through which the blood enters the passage 12, while the manifold 16 likewise contains a plurality of equally spaced holes 24 for the removal of the blood from the blood passage 12. Blood enters the chamber 18 through a pair of apertures 26 and 26' and leaves the chamber 20 through a pair of apertures 28 and 28.

The top side of the plate 10 is grooved around each of the apertures 26, 26', 28 and 28 and circular O-rings 30, 30', 31 and 31 are placed therein. Further, an O- ring 32 is placed in a groove on the plate 10 around the circumference of the blood passage 12 on the top of plate 10.

On the bottom of the plate 10, an O-ring 34 is inserted in a groove around the aperture 26, the circumference of the chamber 18, and the aperture 26. A second O-ring 36 is inserted on the same surface of the plate 10 around the aperture 28, the circumference of the chamber 20, and the aperture 28. In this manner, leakage of the blood from any of its flow pattern is precluded.

Also machined into the plate 10 on the bottom side thereof is a cavity 38 for the passage of water. Water enters the cavity through a hole 40 and leaves the plate 10 through a hole 42. On the top of the plate 10 circular O-rings 44 and 46 are placed in grooves around the holes 40 and 42, respectively, while on the underside of the plate 10 an O-ring 48 is provided around the hole 40, the circumference of the cavity 38, and the hole 42. These O-riugs are provided to prevent leakage of the water from the system.

On the top of the plate 10 a pair of circular O-rings and S0' are placed around gas ports 52 and 52', and circular O-rings 54 and 54 are placed around a pair of gas ports `56 and 56. On the underside of the plate 10 a first O-ring 58 is provided between the gas ports 52 and 52 and a second O-ring 60 is provided between the gas ports 56 and 56. The purpose of these latter O-rings will become apparent as the description proceeds with regard to the second or gas plate which lies on top of the plate 10 to form a module, and the adding of the modules together to form the integrated blood oxygenator.

In FIGS. 3 and 4 there is shown a second plate 62 which is the top plate of a module comprising the two plates 10 and 62 and can be called the gas plate. Formed in the top of the gas plate `62 and extending across a major portion of the width of the plate 62 are a pair of gas manifolds 64 and 66. The gas manifold 64 has a plurality of equally spaced holes 68 contained therein, and the gas manifold `66 has a plurality of equally spaced holes 70 contained therein. The holes 68 and 70 extend the width of the blood passage 12 and lie within this width when the plate 62 is placed on top of the plate 10. As shown in FIG. 4 manifolds 64 and 66 comprise a pair of chambers 72 and '74, respectively. A pair of gas ports 76 and 76 extend through the gas plate 62 into the chamber 72, while a second pair of gas ports 78 and 78 are provided through the plate 62 for connection to the chamber 74.

The plate 62 contains a pair of apertures 80 and 80' which align with the apertures 26 and 26 of plate 10 in the blood flow system, and a second pair of apertures 82 and 82' which align with the apertures 28 and 28 of the plate 10, also in the blood ow system. Finally, a first water hole 84, which aligns with the hole 40 of the plate 10, and a second water hole 86, which `aligns with the hole 42 of the plate 10, are provided in the Plate 62, forming a part of the water flow system.

In FIG. 5 there is shown a cross-sectional View of the plate 62 placed ou the plate 10 to form a module 88 having a semipermeable membrane `90 sandwiched between both plates. The membrane 90 is selected from sheet materials that are pervious to oxygen and carbon dioxide but impervious to blood. Various plastics are suitable for this purpose, such as Teflon or Salistic, or other silicon rubber materials.

Briefly, in the operation of a single module, venous blood is introduced into the chamber 18 of the blood plate 10 and passes through the holes 22 of the manifold 14 into the blood passage 12. While passing through the blood passage 12 carbon dioxide is removed from the thin film of blood which is also oxygenated by oxygen above the membrane 90. The blood leaves the bottom plate 10 through the manifold 16 comprised of the holes 24, and the chamber 20.

Oxygen enters the module 88 through the top plate by way of the chamber 74 of the gas manifold 66, and through the holes 70. After passing across the membrane 90 within the width of blood passage 12, carbon dioxide and any oxygen which is not used up, leave the module 88 through the holes 68 and the gas chamber 72 of the gas manifold 64.

Water passes through the module 88 via hole 40 of FIG. l, along the cavity 38, and exits through the hole 42. The water serves to keep the `blood at the desired temperature level.

Although the membrane oxygenator of the present invention can include a single module, the preferable arrangement is that shown in FIG. 6. A plurality of modules 88, each module consisting of an upper plate 62 and a lower plate 10, are stacked one upon the other and are sandwiched between an upper plate 92 and a lower plate 94. When the modules are thus stacked, it becomes evident that the O-rings which are contained on the bottom of the plate 10 engage with the top of the plate 62 to provide effective fluid seals. Also, the purpose of O- rings 58 and 60 becomes clearer, namely that they seal the circumference of both of the gas manifolds 64 and 66, respectively, of the gas plate 62.

Both the upper plate 92 and the lower plate 94 are adapted for connection to the various Huid lines. In addition, upper plate 92 contains the necessary O-rings for preventing leakage from the gas manifolds 64 and 66 and their associated gas ports 76, 76', and 78, 78'; the pairs of blood apertures 80, and 82, 82'; and the water holes 84 and 86.

To align the plates vertically, a pin 112 is placed into aligning holes 114 and 116 of the plates `62 and 10, respectively, as shown in FIGURE 5. Also, as shown in FIGS. 1 and 3, the plates 10 and 62 contain second aligning holes 118 and 120, respectively, through which a second pin can be inserted to effectively lock the plates and prevent individual horizontal movement of the plates. When the plates are properly aligned, the openings in each plate for the entrance or exit of water, blood and gas are aligned so that single channels are formed for blood entrance, blood exit, gas entrance, gas exit, Water entrance and water exit, respectively.

A continuous strip of membrane material is preferably passed back and forth between alternate pairs of the plates 62 and 10 of the integrated oxygenator without cutting until the desired number of modules are stacked in place.

Referring now to the operation of the integrated membrane oxygenator with the plurality of modules 88, venous blood is introduced into the oxygenator through an opening 96 in the lower plate 94. The venous blood passes to the chamber 18 of the lowermost plate 10 of the modules through a passage in the plate 94 (not shown), across the width of the chamber 18 and then upward through the pairs of apertures 26, 26 and 80, 80 in each of the bottom plates and top plates 62, respectively. At each level of the oxygenator device, the blood is passed up through the blood manifold 14, across the passage 12, and down through the manifold 16 of each module. From each level the blood then passes upward through the pairs of apertures 28, 28 and 82, 82' in each of the plates 10 and 62, respectively, to the upper plate 92. The blood, which can now be considered arterialized, is then removed through a pair of openings 98 and 98' in the upper plate 92.

The oxygenation of the blood is accomplished by passage of oxygen through the oxygenator in a plurality of parallel paths, one path through each of the modules 88. In this manner a large surface area is presented to the oxygen for gas exchange and the number of modules can be increased or decreased as desired for the particular '0b.

J The oxygen flow through the oxygenator is accomplished in the following manner. A uid amplifier 100 passes oxygen from a source 102 to a pair of openings 104 and 104 in the upper plate 92. The pair of openings 104 and 104 are vertically aligned with the pair of gas oprts 78 and 78 of the uppermost top plate 62 of the top module 88. The gas traverses the width of this plate through the gas chamber 74 and proceeds downward l through the gas ports 78, 78 and 56, S6 of each of the top plates 62 and the bottom plates 10, respectively, to the lowermost module. The oxygen also enters the gas manifold 66 of each module 88 and is forced across the membrane 90 in a longitudinal direction.

After oxygenating the blood below each membrane 90, carbon dioxide and any unused oxygen leave each module through the gas manifold 64. These gases then pass upward through the pairs of gas ports 76 and 76', and 52 and 52 of each of the plates 62 and bottom plates 10, respectively, to the upper plate 92. Upper plate 92 contains a second pair of openings 106 and 106 through which the gases pass to be exhausted. As in the case of the blood passage through the oxygenator, it can be seen that a plurality of parallel paths for oxygen ow have been provided by the vertical stacking of the modules between the upper plate 92 and the lower plate 94.

The integrated oxygenator depicted in FIG. 6 has provided therein a heat exchanger for keeping the temperature of the blood regulated at a desired level. The heat exchange function is accomplished by passing water through the modules.

In FIG. 6, for instance, water is pumped into the opening 108 of the lower plate 94 and through a passage (not shown) to the hole of the lowermost module. From this point the Water branches into both the cavity 38 of the bottom plate 10, and the Water hole 84 of the top plate 62, and continues upward through the vertically aligned modules 8-8 through the holes 40 and 84. At each level the water enters the water cavity 38 of each module. After passing through the cavity 38 at each level the water leaves each of the lower plates 10 through hole 42 and proceeds upward through the water hole 86 of each of the top plates 62. An opening 110 is provided in the upper plate 92 for connection to a fitting for removal of the water from the integrated oxygenator. Again, it can be seen that a plurality of parallel paths are provided for the water to perform its heat exchange function.

In operation, water at a desired temperature is allowed to circulate through the water passages in the integrated oxygenator until thermal equilibrium is established. When blood at a different temperature flows through the oxygenator, heat transfer takes place between the water and the circulating blood. The final desired temperature level of the blood can be obtained by adjusting the temperature and flow rate of the circulating water.

With the design of the oxygenator of the present in- Ventron, the gas and blood flows can be made either steady or pulsed. Further, the gas can be controlled above, below, or at atmospheric levels, For operation at pressures below atmospheric, the gas exhaust ports 106 must be connected to a suction line and the inflowing oxygen must be expanded to a pressure near atmospheric before it is introduced into the gas manifolds. Fluid amplifier 100 can be substituted by a gas pump which is adapted to bring the oxygen to the desired atmospheric level `by various venting techniques. If positive gas pressure 1s desired, the inowing gas line from the compressed oxygen source 102 can be connected directly to the gas manifold.

The invention is normally arranged for pulsed operatlon, however. Venous blood under pressure is allowed to enter through the blood inlet 96 into the blood manifold, which distributes the blood to each module. The fluid amplifier 100 is oscillated to create a pulsating gas fiow at the same time the venous blood is introduced. This pulsed gas flow causes the membrane 90 to spread the venous blood into a very thin film in the chamber 12 during the positive phase. Because the blood film is very thin, the gas exchange process takes place rapidly. Upon relaxation of the membrane, new blood is allowed to enter each of the blood channels in the modules and the carbon dioxide and unused oxygen leave the integrated oxygenator through the gas outlets 106. Consequently, a new film of blood is brought into contact with the membrane at each gas pulse.

A unique feature of the subject invention in the normal pulsed operation, or even in steady gas flow operation, is that a chamber is not required in the gas plate 62. The pressure of the oxygen forces membrane 90 down into blood passage 12, thereby creating a very thin film of blood as well as providing a shallow passage for the gas along the length of the gas plate 62 between the plate itself and the top of the membrane 90. Since the holes 68 and of the gas manifolds 64 and 66, respectively, are restricted to the Width of the blood passage 12, it can be seen that gas leakage between the membrane and the gas plate 62 is prevented by the sealing action ofv O-ring 32 which forces the membrane 90 into gas-tight engagement with the plates 62.

For ease of assembly, the integrated oxygenator of FIG. 6 is designed so that a role of membrane material can be sandwiched between each of the upper and lower plates without cutting or sealing, until the desired number of modules are stacked in place. Once the desired number of modules are placed between the upper plate 92 and the lower plate 94 various clamping means can be employed to hold the unit together and also seal the membranes. Since all the O-rings are employed on the bottom plate 10 it can be seen that upon clamping, each of the passages in each of the modules are made leak proof.

If the extra-corporeal circulation device of the present invention is desired to be used as a dialyzer, such can be accomplished by merely forming a small passage in the top plate 62, similar to the blood passage 12 in the lower plate 10.

As an added feature the design of the instant invention potentially allows the modules to be molded of disposable plastic.

The above description is of a preferred embodiment of the invention, and manv modifications may be made thereto without departing from the spirit and scope of the invention, which is defined in the appended claims.

What is claimed is:

1. A blood oxygenator comprising a first plate having a shallow cavity defining a blood passage on one surface thereof, a second plate having two flat opposed surfaces, membrane sandwiched between said plates enclosing the cavity of said first plate, said membrane being pervious to oxygen and carbon dioxide but impervious to blood, apertures formed in the first plate on [both ends of said cavity to provide an entrance and exit for blood flow through said cavity, ports formed in said second plate at substantially the ends of the cavity to provide an entrance and exit for oxygen gas fiow between said second plate and said membrane, and sealing means around the circumferenece of the cavity, said sealing means defining a gas passage on the second plate when both plates and the membrane are placed together.

2. A blood oxygenator as defined in claim 1, further comprising a second open cavity formed in said first plate on the other surface thereof, and holes formed in said first plate to provide an entrance and exit for water flow through said second cavity.

3. A .blood oxygenator comprising a pl-urality of -first plates having a shallow cavity defining a blood passage on one surface thereof, a plurality of second plates having two fiat opposed surfaces, a membrane sandwiched between said plates enclosing said cavity of said first plates, said membrane being pervious to oxygen and carbon dioxide but impervious to blood, apertures formed in the rst plates on both ends of said cavity to provide an entrance and exit for blood fiow through said cavity, ports formed in said second plates at substantially the ends of the cavity to provide an entrance and an exit for oxygen gas flow between said second plates and said membrane, and sealing means around the circumference of said cavity, said sealing means defining a gas passage on the second plate when both plates and the membrane are placed together, said plurality of pairs of plates being stacked to provide a plurality of parallel blood and oxygen fiow paths with said apertures and ports being aligned to form single channels for blood entrance, blood exit, gas entrance and gas exit, respectively.

4. A blood oxygenator as defined in claim 3, further comprising an upper plate and a lower plate sandwiching said stacked pairs of plates, said upper plate being adapted for connection to an oxygen source and said lower plate being adapted for connection to a blood source.

5. A blood oxygenator as defined in claim 4, further comprising a fluid amplifier oscillator connected to said upper plate for providing pulses oxygen for pulsed operation of the oxygenator.

6. In a membrane oxygenator of the type including a pair of plates having a membrane sandwiched therebetween, the improvement comprising a shallow cavity defining a blood passage on one of said plates on its operating surface adjacent to said membrane and sealing means around the circumference of said cavity, said sealing means cooperating with said membrane to define a passage for gas on the surface of the other of said plate, between said other plate and said membrane.

7. On eXtra-corporeal circulation device comprising a first plate having a shallow cavity on one surface thereof, a second plate having opposed fiat surfaces, a membrane sandwiched between said plates enclosing the cavity of said first plate, and sealing means provided on said first plate around the circumference of said cavity, said sealing means defining a passage on the fiat surface of said second plate when both plates and the membrane are placed together.

8. An extra-corporeal circulation device as defined in claim 7, further comprising an open second cavity formed in the opposite surface of said first plate, said second cavity forming another fiuid passage.

References Cited UNITED STATES PATENTS 3,208,448 9/1965 Woodward 12S-l 3,212,498 10/1965 McKirdy et al 23-258-5 2,712,386 7/1955 Jones et al 210-321 XR 3,131,143 4/1964 Ferrari 210-321 XR 3,332,746 7/1967 Claff et al. 23-258.5

OTHER REFERENCES Crescenzi et al.: Apulsatile Extracorporeal Membrane System, Proc. of the San Diego Symposium for Biomedical Eng. (1963), pp. 27-31 and cover.

Claff et al.: Apulsatile Pressure Transport System Across Artificial Membranes, Proc. of the 16th Ann. Conf. on Eng. and Biology (vol. 5), Baltimore, Md., Nov. 18-20, 1963, pp. 114-115 and cover plus unnumbered pages.

Vadot et al.: Trans Amer. Soc. Artif. Int. Organs, (1964), pp. 121-126.

I AMES H. TAYMAN, J R., Primary Examiner.

U.S. Cl. XR. 

